The interior of the ATS, which shows off the plethora of buttons on the steering wheel and the infotainment system.

Ron Amadeo

The main screen of the infotainment system.

Ron Amadeo

The map application.

Ron Amadeo

NEW YORK CITY—The world's fastest mobile hotspots? General Motors is bringing mobile connectivity to most of its 2015 car lineup with a service called "OnStar 4G LTE." As the name would imply, GM is integrating an LTE modem into its vehicles as a standard feature, giving owners a mobile data connection wherever they are. GM invited us down to SoHo's Classic Car Club to demo the feature on a 2015 Cadillac ATS.

Why would you want to get LTE through your car instead of through a portable hotspot or your smartphone? The simple answer is that a hotspot in a car can get much better reception. On the roof of the ATS is a "shark fin" antenna, similar to what has been used in the past for satellite radio. The antenna picks up LTE, carries it to the car infotainment system, and beams it via Wi-Fi to up to seven devices in your car.

The roof-mounted antenna benefits from being not just higher up than a smartphone, but it's outside of the potential signal killer that is a car. The antenna can also be better at picking up a signal than a smartphone. Smartphone antennas need to fit into a pocket-sized device and can only sip power from the tiny battery. A car antenna only needs to fit into several thousand pounds of vehicle and is eventually powered by gasoline, so there is much more room for a performance improvement. If you're in an area with a weak signal, the car has a much better chance of getting a signal than your phone.

Besides beaming Internet to all your devices, integrated mobile data also means the car's infotainment system can access the Internet without having to be connected to your smartphone. This doesn't make much of a difference when you are in the car, but it means you can talk to the car when you are away from it. With the "OnStar RemoteLink" mobile app, you can see your car's gas (or battery) level, tire pressure, and perform key fob functions, like lock, unlock, and remote start over the Internet. Third-party key fobs often tout the range of their devices, but when you're doing things over the Internet, the range is virtually unlimited.

Taking full advantage of the hotspot LTE access will basically require a separate device. The Cadillac's in-car infotainment system runs Pandora and not much else. While the modern data connection is there, the software that runs on it is still stuck in the past.

GM says that the LTE integration is just the start of its move to modernize the car interior, and the company says it is exploring things like an app store. And if GM's in-house efforts don't work out, the company has also committed to Apple's CarPlay and Google's Android Auto in future models.

So how much will this cost?

OnStar 4G LTE Data Pricing

Data/Month

200MB

1GB

3GB

5GB

OnStar Subscriber

$5

$15

$30

$50

Non-Subscriber

$10

$20

$30

$50

The downside to this integration is that yes, your car will be another device with a monthly data bill. The good news is that, initially at least, you only have to pay for the mobile hotspot service—all the key fob and car information services are free for five years.

Existing AT&T subscribers can add their car to a Mobile Share Value plan for $10, or users can buy AT&T data from OnStar directly, which is in the table on the right. There are also non-monthly plans: $5 for 250MB that expires after a day or $200 ($150 for OnStar subscribers) for 10GB that expires in 12 months.

A big part of the Internet of Things is going to involve putting a cellular modem in just about everything. For now, though, the wireless carriers' insistence on attaching an additional fee to everything puts a bit of a downer on an innovative idea.

If you don't mind the monthly bill, the potential for a serious signal improvement is there. While we would have loved to test the reception during our brief hands-on time, everything we owned was already saturated in signal in the middle of SoHo. The performance of the system is something we'll revisit in the future when we spend more time with the car in the wild.

Ron Amadeo
Ron is the Reviews Editor at Ars Technica, where he specializes in Android OS and Google products. He is always on the hunt for a new gadget and loves to rip things apart to see how they work. Emailron@arstechnica.com//Twitter@RonAmadeo